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1. Lynbrook West, an apartment complex, has 100 two-bedroom units. The monthly p

ID: 2860843 • Letter: 1

Question

1. Lynbrook West, an apartment complex, has 100 two-bedroom units. The monthly profit (in dollars) realized from renting out x apartments is given by the following function.

P(x) = 12x2 + 1992x 53,000

To maximize the monthly rental profit, how many units should be rented out?

What is the maximum monthly profit realizable?

2. The average speed of a vehicle on a stretch of Route 134 between 6 A.M. and 10 A.M. on a typical weekday is approximated by the function

f(t) = 23t 46sqroot(t)+ 56    (0 t 4)

where f (t) is measured in miles per hour, and t is measured in hours, with t = 0 corresponding to 6 A.M. At what time of the morning commute is the traffic moving at the slowest rate?

What is the average speed of a vehicle at that time?

Explanation / Answer

1) 0<=x<=100

P(x) = 12x2 + 1992x 53,000

for local maximum dP/dx =0

dP/dx =-24x +1992 -0 =0

=>x =1992/24

=>x =83

P(0)=0+0 -53000=-53000

P(83)=12*832 + 1992*83 53,000=29668

P(100)=12*1002 + 1992*100 53,000=26200

To maximize the monthly rental profit, 83 units should be rented out